The use of endoscopes for diagnostic and therapeutic indications is rapidly expanding. To improve performance, endoscopes have been optimized to best accomplish their purpose. Therefore, there are upper endoscopes for examination of the esophagus, stomach and duodenum; colonoscopes for examining the colon; angioscopes for examining blood vessels; bronchoscopes for examining the bronchi; laparoscopes for examining the peritoneal cavity; and arthroscopes for examining joint spaces. The discussion which follows will apply to all of these types of endoscopes.
Instruments to examine the rectum and sigmoid colon, known as "flexible sigmoidoscopes," are good examples of the usefulness of endoscopic technology. These devices are expensive, and they are used in a contaminated environment for a procedure which is brief (five to ten minutes) and where problems of cleaning time and contamination are important factors. There has been a large increase in the use of the flexible sigmoidoscope for use in screening symptomatic and asymptomatic patients for colon and rectal cancer. Ideally, flexible sigmoidoscopes must be used rapidly and inexpensively in order to maintain the cost of such screening at acceptable levels. Typically, a clinic would like to perform five sigmoidoscope examinations each hour. A significant problem with making such examinations quick and inexpensive is the time necessary for adequately cleaning the device.
Although endoscopes can be cleaned in about two to four minutes, this relatively cursory cleaning may not be adequate for complete disinfection or sterilization. Even a more complete cleaning, requiring on the order of eight to ten minutes, may not allow adequate cleaning, particularly in view of the increasing problems with contagious viruses. Even with the use of chemicals such as gluteraldehyde, adequate cleanliness may not be possible.
The cleaning problem not only includes the outside of the endoscope but also the multiple small channels inside the endoscope. This includes channels for: air insufflation; water to wash the tip; and biopsy and suction. Each channel also has a control valve. These channels extend along the length of the endoscope and come into contact with body tissues and fluids. It is extremely difficult to adequately clean these channels even when skilled health practitioners spend a great deal of time on the cleaning procedure.
Even if endoscopes can be adequately cleaned in eight to ten minutes, the cleaning still prevents endoscopy examinations from being relatively inexpensive. While a physician may spend five to ten minutes performing some types of endoscopy, he or she will generally waste a great deal of time waiting for the endoscope to be cleaned before he or she can conduct another endoscopy. A partial solution to the "idle time" problem is to purchase multiple instruments so one can be used as the others are being cleaned. However, the expense of having duplicate endoscopes of each of the many types described above makes this solution impractical, especially for physicians' offices and smaller clinics.
Not only must the idle time of the physician be added to the cost of endoscopic examinations, but the time spent by a nurse or other hospital personnel in the cleaning as well as the cost of disinfecting chemicals and other costs of the cleaning process must also be added to the cost of the examination. Although automatic washing machines are available to clean endoscopes, these machines are expensive, take up significant amounts of space, are noisy and are not faster than washing by hand. Further, regardless of whether the cleaning is done manually or by machine, the cleaning chemicals can be harmful to the endoscope and thus significantly shorten its life. The cleaning chemicals, being toxic, are also potentially injurious to the staff who use them and to the environment into which they are discharged. To use some of these chemicals safely, such as gluteraldehyde, requires a dedicated ventilated hood, which uses up space and is expensive to install and operate. The chemicals are also potentially toxic to the patient in that, if residue remains after cleaning and rinsing the instrument, the patient could have a reaction to the chemicals.
As a result of these many problems, conventional endoscope cleaning techniques greatly increase the cost of endoscopic procedures. Furthermore, while the risk of contamination using endoscopes is often far less than the risk of alternative procedures, such as surgery, there is nevertheless a risk that endoscopes are not cleaned adequately to prevent the risk of transmission of infectious diseases from one patient to the next.
In the health care field, the problems of contaminated instruments transmitting disease from one patient to the next have generally been solved by making such instruments disposable. However, this approach has not been thought possible in the field of endoscopy because endoscopes are very expensive instruments. Moreover, it has not been thought possible to isolate the endoscope from the patient or the external environment because the endoscope itself has channels inside it that are used as a conduit for body fluids and tissues, such as, for example, in taking biopsies. The only method currently available to actually sterilize an endoscope is to use gas sterilization with ethylene oxide gas. However, there are several disadvantages in using this procedure. The procedure is very slow (up to 24 hours), during which time the endoscope cannot be used. Also, the gas affects the plastic of the endoscope and may limit its lifespan. Finally, the gas is toxic, and, therefore, great care must be taken to ensure that no residue remains that might cause patient or staff irritation or allergic reaction during contact with the endoscope.
As a result of the above-described limitations in using and cleaning endoscopes by conventional techniques, there has not heretofore been an acceptable solution to the problem of making endoscopy procedures both inexpensive and entirely safe.
A new approach to the problem of endoscope contamination is described in U.S. Pat. No. 4,646,722. This new approach involves the use of an endoscope sheath having a flexible tube surrounding the elongated core of an endoscope. The flexible tube has a transparent window near its distal end positioned in front of the viewing window of the endoscope. Channels that come into contact with the patient or the patient's body fluids (e.g., channels for taking biopsies, injecting air or injecting water to wash the window of the sheath) extend along the endoscope, either inside or outside the sheath. Where the channels are positioned inside the sheath, they may be inserted in a longitudinal groove formed in the endoscope core. The protective sheath may be used with either end-viewing endoscopes or side-viewing endoscopes. The protective sheath may be installed by rolling the elastomeric tube or casing into an annular configuration and then unrolling the tube over the core of the endoscope. Alternatively, the tube may be inflated in its unrolled configuration to expand the tube and allow it to be easily slipped onto the endoscope core. A variety of specialized endoscopes may be created by using protective sheaths having a variety of special purpose medical instruments mounted at the end of a biopsy channel and operated through the channel.
After use of the endoscope, the sheath and channel insert are removed and disposed of, leaving the endoscope free of contamination resulting from the endoscopic procedure. An essential aspect of this approach is incorporating the channels into the system so that the flow of air or liquids through the channels can be controlled without spreading contamination. These channels are essential for many types of endoscopy. In gastroenterology, the channels are used for insufflation of air to open the otherwise closed lumen of the intestinal organs, for spraying water over the tip lens to clean off obscuring mucus, stool or blood, and for suctioning fluid, blood or mucus which is obscuring the examination. The suction channel is the same channel used in most designs for passage of a variety of instruments for diagnosis (biopsy forceps, brushes for cytology, etc.) and therapy (snares to remove polyps, probes to stop ulcer bleeding, etc.).
All of the above-described channels are contaminated in the course of an endoscopy. In the currently used endoscopes (fiberoptic and video), these channels and their valves are the most difficult portions of the endoscope to clean. The suction channel is grossly contaminated with secretions including blood, mucus and stool in every case. A valve in continuity with the inside of the channel is also instantly contaminated. The air and water channels present slightly different problems. The direction of the flow of the air and water is towards the end of the endoscope. Therefore, one might think that these channels could not become contaminated. In fact, however, because of capillary action as well as gravity, both of these small channels are always contaminated with secretions during endoscopy, including blood, stool and mucus. Further, the small size of these channels makes them very hard to clean. If any residue remains, the residue can react with gluteraldehyde, which is commonly used to clean the channels, to produce a thick substance that can plug the channel. This plug is very difficult to remove and sometimes requires that the endoscope be returned to the manufacturer for replacement of the channel. Each of the channels (air and water) also has a valve control which is in continuity with the channel and is potentially contaminated during endoscopy.
The disposable endoscope sheath described in U.S. Pat. No. 4,646,722, which is incorporated herein by reference, reduces the contamination caused by these channels and their valves. With this protective sheath, the air, water and suction channels are entirely disposable. However, it is essential to be able to control flow through these channels to be able to perform endoscopy. Therefore, it is necessary to be able to control the flow of air or liquid through these channels yet be able to dispose of all contaminated components after the procedure. It is therefore important that the valve mechanism controlling the flow of air or liquid through the channels not touch the inside of the channel. As a result, contamination of the valves cannot occur.
An additional requirement for a valve system for the channels is that the valve be located between the contaminated distal area of the tube and the pump portion (for air and water channels) so that contamination cannot get back past the valve to the source of the air and water. For the suction channel, the system incorporates a suction trap (which is routinely used with current endoscopes). The direction of flow of the suction is towards the trap. With the disposal of contaminated tubing and the use of a clean trap for each patient, contamination of the next patient is not possible.
A final requirement of a valve system for the endoscope channels is that it be easily used by endoscopists. Thus, the valve system must allow accurate control of air, water and suction. Furthermore, it should be actuated by essentially the same type of control motions with which endoscopists have become familiar. Ideally, the valve system should have the same "feel" as conventional endoscope valve systems so that the endoscopist will scarcely be aware that he or she is using a specially designed valve system.